The invention relates to a method of recording information on a record carrier, in which an information signal is converted into a code signal comprising code words made up of bits, the number of successive bits of a first logic value being at least equal to P and groups of at least P bits of a first logic value within each code word being separated by at least Q successive bits of a second logic value, P being an integer greater than or equal to 1 and Q being an integer greater than P, in which method a pattern of recording marks corresponding to the code signal is formed on the record carrier, the recording marks representing the bits of the first logic value.
The invention also relates to a device for recording information on a record carrier, which device comprises an encoding circuit for converting an information signal into a binary code signal made up of code words, the number of successive bits of a first logic value in each code word being at least P and groups of at least P bits of the first logic value being separated by at least Q successive bits of a second logic value, P being an integer greater than or equal to 1 and Q being an integer greater than P, the device further comprising drive means for moving the record carrier relative to the write means, the write means being adapted to form an elementary mark on the record carrier in response to a code-signal bit of the first logic value.
The invention further relates to a record carrier provided with an information track in which information is recorded as an information pattern of recording marks, the information pattern comprising code symbol which represent code words. The code symbols occupy substantially equidistant symbol positions, a number of said positions being occupied by a recording mark, and the number of successive symbol positions occupied being at least equal to P and the number of non-occupied successive symbol positions within the code symbols which are situated between the group of occupied symbol positions being at least equal to Q, P being an integer greater than or equal to 1 and Q being greater than P.
Moreover, the invention relates to a device for reading the record carrier.
In addition, the invention relates to an encoding and decoding circuit for use in the recording and read device.
Said method, record carrier, recording and read device are known, inter alia from British Patent Specification-GB 2,148,670.
In the method and the recording device described therein 8-bit information words of the information signal are converted into 15-bit code words, the number of successive "1" bits being at least 1 and the number of successive "0" bits being at least 2.
When the record carrier is read the pattern of recording marks is scanned by a laser beam, the reflected laser beam being modulated by the pattern being scanned. An optical detector detects the reflected laser beam to generate a detection signal of a signal strength corresponding to the degree of modulation of the laser beam. Subsequently, the code signal is recovered from the detection signal. In order to ensure a reliable detection the code words should meet the additional requirement that the number of "1" bits is 4 for every code word. In that case every code word can be recovered reliably from the detection-signal portion corresponding to said code word by selecting the four positions of most extreme signal strength in the detection signal. Such a detection method is known as differential detection.